The present invention pertains to a multiple cable suspension system used to support the boom extending from an earth moving shovel. The invention is particularly applicable to such shovels which are used in mining ore where the shovels used are massive and the booms are required to support enormous weights. In such mining shovels the boom is generally pivotably supported at its lower end by the base of the shovel and is supported at its extended end by suspension cables secured to a rigid gantry.
When a plurality of suspension cables are used it is desirable to have the load on the cables evenly distributed between the cables, and therefore each of the cables must be exactly the same length or means must be provided to compensate for differences in the lengths of the cables.
It has proved desirable in some applications to use preformed cable assemblies having predetermined lengths and including sockets at each end to facilitate relatively easy connection to the boom and gantry. Suspension cables of such fixed lengths have been used in the prior art, but some problems have remained because the cable assemblies including sockets attached to each end cannot be fabricated in lengths having tolerances of less than plus or minus one-fourth of an inch, such tolerances thereby allowing two cables to differ in length by as much as one-half of an inch. When cables are used having such discrepancies in length, the shorter cables absorb the tensile stress, and the remainder of the cables are slack. As is readily apparent, these drawbacks are particularly acute when the boom is of such size as to require the use of four suspension cables rather than merely two.
In the prior art, attempts have been made to provide means for attaching the cables to the boom and the gantry to compensate for diversities of length of the cables. However, the prior art apparatus has proved to be somewhat complicated and costly.